From pluto at projectpluto.com  Fri Jul  9 12:49:17 2021
From: pluto at projectpluto.com (Bill Gray)
Date: Fri, 9 Jul 2021 12:49:17 -0400
Subject: [neo_followup] OCA0580 = interesting object
Message-ID: <4c0b3dfe-3364-64d6-2997-2c14db79f329@projectpluto.com>

Hello all,

    This object currently has three tracklets on NEOCP.  (X74)
got it on 7.14 July.  A day later,  it and (W85) got it almost
simultaneously,  but about 20' apart.  At least one of those
two tracklets is wrong.

    I have strong doubts about the (W85) tracklet.  It's less
than five minutes long and just barely shows motion (about
2.3") to be believed.  It's a recipe for a bad linkage.  But
you can link it to the first arc and get plausible,  mundane
orbits.  The uncertainties are low enough that it should be
easy to find,  or rule out,  this possibility.

https://www.projectpluto.com/temp/mpec2.htm

    (X74)'s tracklets are both about 24 minutes long,  showing
decent motion,  and they link well.   If correct,  they would
indicate a close flyby at 60000 +/- 20000 km within a day
or so of July 11.5,  reaching peak magnitude of about 11.7 :

https://www.projectpluto.com/temp/mpec.htm

    That would be just enough of a "zebra" to give me doubts
about _that_ tracklet,  too,  but if it's correct,  it very
much merits some follow-up.  Being (much) closer,  the
uncertainties are larger and growing quickly.

    MPC's ephemerides appear to assume that all six (X74)
observations are correct,  i.e.,  the second of the two
solutions shown above.

-- Bill